JPH0346419Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Technical Field of the Invention) The present invention relates to an improvement of a power cable whose main insulator is a wound layer of laminated paper.

(Technical background of the invention and its problems) Conventionally, as a paper insulated power cable, unit tapes 1a to 1d made of several to ten or more sheets of insulating paper are wound alternately on a conductor 2, as shown in Fig. 1. What happens is known.

By the way, in such paper-insulated power cables, if a laminated paper made by laminating kraft paper and plastic film is used as the insulating paper, the peel strength of this tape is not so high, so as shown in Figure 2. As shown in FIG. 3, the laminated kraft paper 4 peels off between adjacent unit tape layers, that is, at a portion 3 where the winding directions of the unit tape are opposite to each other (hereinafter referred to as layer change portion). This phenomenon (hereinafter referred to as "fighting") occurs, and the area becomes an electrical weak point, and the folded kraft paper impedes the smooth sliding of the paper due to thermal expansion and contraction, causing so-called soft spots in other areas. There was an inconvenience that caused a weak point to occur.

(Purpose of the invention) The present invention has been made with attention to these points, and is intended to provide a power cable that can eliminate the fighting phenomenon of laminated paper at the layer change portion.

(Summary of the invention) In the present invention, the above object is achieved by inserting at least one insulating tape in the layer change portion of the unit tape.

(Embodiment of the invention) Hereinafter, the invention will be described based on the drawings of one embodiment. In FIG. 4, a unit tape 8a made up of multiple sheets of laminated paper 7 made of kraft paper 5 and plastic film 6 is wound in a fixed direction onto a conductor by one paper wrapping head, and then by another paper wrapping head. Another unit tape 8b is wound in the opposite direction to the winding direction of the previous head. Third,
Unit tapes (not shown) having four or more layers are also wound in opposite directions as described above.

Thus, at least one insulating tape 9 is inserted above and below the unit tapes 8a and 8b, that is, at the portion corresponding to the layer change portion. As the insulating tape 9, a material having good electrical insulation properties and high tensile strength, such as kraft paper, is suitable. Instead of kraft paper, a laminate tape in which silicone-grafted polyethylene is chemically bonded to one side of kraft paper may be used.

An insulating tape with good insulation properties and high tensile strength is used because the tape itself constitutes a part of the cable insulation, and due to the above-mentioned fighting phenomenon at the layer change part, the laminated paper, which is the main insulator, is used. This is to prevent peeling from occurring.

Note that this insulating tape may be provided between the conductor-side and insulation layers or between the insulation-side and insulation layers.
A laminate tape with high peel strength may be inserted between the unit tape layers, and kraft paper may be inserted between the unit tape layers and the stiff layer.

(Effects of the invention) As described above, in the present invention, an insulating tape that is not likely to peel off is inserted into the layer change part of the unit tape, so the insulating tapes face each other in the layer change part and are held together. Therefore, it is possible to provide a power cable that can eliminate the peeling phenomenon of laminated paper.

Furthermore, in the present invention, since the number of insulating tapes such as kraft paper is small, there is no need to worry about significantly impairing the low loss (dielectric loss) characteristic of laminated paper insulation.

[Brief explanation of the drawing]

Figure 1 is a schematic cross-sectional view of a power cable;
The figure is an explanatory diagram showing the layer change part, Fig. 3 is an explanatory diagram showing the peeling situation of the laminated paper, and Fig. 4 is a partially omitted cross-sectional view enlarging only the unit tape and insulating tape, which are the characteristic parts of the present invention. It is. 7... Laminated paper, 8a, 8b... Unit tape, 9... Insulating tape.

Claims (1)

[Claims for Utility Model Registration] 1. In a power cable formed by unit tapes made of multiple sheets of laminated paper wound alternately around a conductor, between adjacent layers of the unit tapes:
A power cable characterized by interposing at least one insulating tape with good insulation properties and high tensile strength. 2. The power cable according to claim 1, wherein the insulating tape is made of kraft paper. 3. The power cable according to claim 1, wherein the insulating paper is made of kraft paper and a silicone-grafted polyethylene film chemically bonded to one side of the insulating paper.